Extreme pressure lubricants containing highly oxidized waxes



United States Patent Qfilice Patented June 25, 1963 3,095,375 EXTREME PRESSURE LUBRICANTS CONTAINING HIGHLY OXIDIZED WAXES Herbert J. Pitman, Jefferson, Tex., assignor to Texaco Inc., a corporation of Delaware N Drawing. Filed June 24, 1958, Ser. No. 744,293 14 Claims. (Cl. 252-28) This invention relates to improved lubricating compositions and more particularly to lubricating compositions of improved extreme pressure properties containing small amounts of certain highly oxidized waxates.

Petroleum oxidates of various types have been employed heretofore in lubricating compositions for various purposes, for example as rush inhibitors, viscosity improv ers and oiliness agents to improve the lubricity and anti- Wear properties of the compositions. The oxidates thus employed have been products obtained by oxidizing petroleum fractions to a relatively limited extent or under conditions which result in either polymerized or estertype products, in order to obtain both maximum oil solubility and effectiveness for the particular purpose. The oxidates employed as oiliness agents have been generally oxidized parafiinic hydrocarbons or separated fractions thereof, obtained by carrying out the oxidation under conditions giving a product having a neutralization number usually below about 100, in order to obtain a maximum concentration of oil soluble fatty acids and their esters, since both the oil solubility andoiliness improving property of the oxidates decrease with increasing concentration of more highly oxidized compounds.

It has now been found, in accordance with this invention, that wax oxidates of a particular type impart improved extreme pressure properties to mineral lubricating oil compositions when they are incorporated therein in minor proportions. The oxidates having this property of imparting extreme pressure properties to lubricant compositions are highly oxidized Waxates, obtained by oxidizing macrocrystalline paraffin waxes up to neutralization numbers of at least about 200, such as neutralization numbers in about the range 200-550, and under conditions which produce a low viscosity acid-type product, having a ratio of neutralization number to saponification number above 0.5.

The extreme pressure eifect obtained with these highly oxidized waxates is not obtained with petroleum oxidates which have been employed heretofore as lubricant additives including oiliness agents, such oxidates merely improving the lubricity and anti-wear properties of the compositions similarly to the naturally occurring fatty acids and their esters. The extreme pressure properties of a lubricating composition depend upon its ability to maintain a thin protective coating upon a metal surface, usually considered to be by chemical reaction therewith, at pressures above those at which an ordinary lubricant film is maintainable. The eifect of an extreme pressure additive is therefore different from that of an oiliness or anti- Wear agent, which merely increases the film strength of the composition so as to prevent rupture of the lubricating film at ordinary or moderately increased pressures.

The oxidates employed in accordance with this invention are produced by the method which comprises blowing air through a par-affin wax charge while the charge is maintained at an elevated temperature in the range from about 200 F. to about 400 F. and under an increased pressure in the range from slightly above atmospheric up to about 500 pounds per square inch, with an air feed rate from about to about 60 cubic feet of air per hour per pound of wax charge. Suitable feed stocks for this reaction are waxes. separated from parafiinic distillate oils such as a crude scale wax or slack wax, preferably containing not more than about 20 percent by weight of oil, and most advantageously containing not more than "about 10 percent by Weight of oil. The reaction is preferably carried out at a temperature in about the range 250 vF.350" F., most suitably in about the range 270 F.-330 F., and under a pressure in about the range 30- 300 pounds per square inch, most suitably in about the range 50250 pounds per square inch gauge. An oxidation catalyst is preferably employed when the reaction is carried out at pressures below about pounds per square inch or when the wax charge contains more than about 5 percent by weight of oil. The preferred catalyst is a metal permanganate, most suitably potassium permanganate, which may be employed in an amount from about 0.01 to about 1.5 percent by weight of the wax charge.

Under the above conditions, the reaction consists almost entirely of formation of oxygenates of various types with no more than a small amount of polymerization, the neutralization and saponification numbers of the wax charge increasing rapidly up to very high values while the viscosity increases only very slowly up to a viscosity Saybolt Universal at 210 F. of less than 500 seconds, and usually to less than about 200 seconds. The products formed in the first stages of the oxidation reaction are largely simple alcohols, aldehydes, ketones, acids and esters. As the oxidation proceeds further, the formation of more highly oxidized products takes place at increasing rates, and the highly oxidized products obtained by carrying out the oxidation to neutralization numbers of about 200 or highertherefore contain relatively large amounts of oxygenated fatty acids such as hydroxy fatty acids, keto fatty acids and dicarboxylic acids. These highly oxidized products contain relatively large amounts of low molecular weight oxygenates, containing about 1-3 carbon atoms per molecule, including low molecular weight acids, aldehydes, ketones, etc., formed by degradation reactions. This low-molecular weight fraction has little or no effectiveness for improving the extreme pres sure properties of lubricating compositions, and may be separated by any suitable means such as by distillation or extraction from the higher molecular weight oxidate fraction employed in accordance with this invention. However, the crude oxidate may be employed for the sake of convenience when the presence of such compounds in the lubricant composition is not objectionable. The preferred oxidate materials for use according to this invention are those containing only minor amounts of such low molecular weight oxygenates or fractions from which such oxygenates have been removed, as by water washing, which results in a lowering of the neutralization number to within about the range 150450. Particularly preferred oxidate materials are higher molecular weight fractions having neutralization numbers of at least about 200, obtained by water washing wax oxidates having neutralization numbers in about the range 250-550, and having a ratio of neutralization number to saponification number of at least about 0.6.

The lubricating compositions of this invention comprise a mineral lubricating oil as the chief component having incorporated therein a small amount of a wax oxidate fraction of the character described above, in sufficient amount to impart increased extreme pressure properties to the composition. Ordinarily the amount of wax oxidate will be in the range from about 2 to about 10 percent by weight of the composition, although somewhat smaller or larger amounts may be employed in some cases, such as, for example, amounts from about 0.5 to about 15 percent by weight of the composition. The composition may also contain gelling agents of various types, including the conventional fatty acid soaps, such as for example, sodium stearate, sodium myristate, lithium 12-hydroxystearate, calcium 12-hydroxystea-rate, etc.,

and finely divided solids having the property of thickening lubricating oils, including inorganic materials of various types, and organic materials such as high molecular weight polymers and certain pigments such as indigo and the phthalocyanines. Such materials may be present in very small amounts or in grease forming proportions. Ordinarily where materials of this character are employed they will be present in amounts from about 5 to about 35 percent by weight, although smaller or larger amounts may be employed in some cases, such as for example, from about 2 to about 45 percent by weight based on the weight of the composition.

Other additives of the usual types may also be employed in these compositions, such as oxidation inhibitors, corrosion inhibitors, anti-wear agents, viscosity index improvers, and other extreme pressure agents. With particular advantage, the lubricating compositions of this invention may contain a minor but substantial amount, such as about 2-20 percent by weight and preferably about 5-15 percent by weight, of a sulfurized fatty oil, such as, for example, sulfurized castor oil, sulfurized lard oil, sulfurized sperm oil, sulfurized fish oils, or the like, containing about 5-15 percent by weight of sulfur. By employing an oxidate of the character described above together with a sulfurized fatty oil, extreme pressure properties are imparted to mineral lubricating oil compositions which are substantially higher than those obtainable with either of these materials employed separately as the sole extreme pressure additive, and accordingly the use of a material of each of these two classes in combination in mineral lubricating oil compositions comprises a preferred embodiment of this invention.

The lubricating oils employed in these compositions may be any mineral oils in the lubricating oil viscosity range, such as oils having viscosities in the range from about 80 seconds Saybolt Universal at 100 F. to about 225 seconds Saybolt Universal at 210 F., obtained by any of the conventional refining procedures from paraffinic, naphthenic or mixed base crudes, including straight mineral oils, distillates and residuals, as well as blends of such oils.

A particularly valuable application of this invention is found in imparting improved extreme pressure properties to solids thickened greases, wherein a softening or breaking down of the grease structure is produced by the addition of many otherwise effective extreme pressure agents. I have found that by the addition of small amounts of oxidates of the character described above, very superior extreme pressure properties are imparted to these greases with little or no softening and no impairment of the grease structure.

A preferred class of inorganic gelling agents for producing lubricating greases in accordance with this invention comprises inorganic colloidal materials such as silica gel and metal silicates such as bentonite, metal oxides such as magnesium oxide, etc., having at least a substantial part of their surface, such as at least about 5 percent and preferably at least about 30 percent, coated with organic hydrophobic surface active compounds, which may be either merely adsorbed upon their surface, as described by F. H. Stross et al. in U.S. 2,658,869, or combined therewith by chemical reaction, as described, for example, by J. W. Jordan in US. 2,531,440. The preferred compounds of the latter type are the so-called onium clays, obtained by a base exchange reaction between a clay and a quaternary ammonium compound, preferably having at least one aliphatic hydrocarbon substituent group of ten or more carbon atoms, such as for example, dimethylethyldodecyl ammonium hydroxide, dimethylbenzyllauryl ammonium chloride, triethyloctadecyl ammonium chloride, etc. The reaction is preferably carried out employing at least about 40 percent, and most suitably at least about 70 percent by weight of the quaternary ammonium compound theoretically required The following examples are given for the purpose of further disclosing the invention.

EXAMPLE I A grease representative of the lubricating compositions of this invention is obtained from the following materials in the indicated proportions in percent by weight:

Organo-clay 8.0 Oxidate 5.0 Mineral lubricating oil Remainder The organo-clay is a micron sized bentonite which has been treated with dimethyldistearyl ammonium chloride in alcohol solution, employing stoichiometric proportions of the reactants on the basis of the measured base exchange capacity of the bentonite.

The oxidate is the water insoluble fraction of a crude oxidate material obtained by oxidizing a semi-refined 127 F. melting point w-ax containing about 0.4 percent by weight of oil, from a paraffinic distillate fraction. The oxidation is carried out in an aluminum reactor by passing air through the Wax containing 0.4 percent by weight of potassium permanganate at 270 F. under a pressure of 75 pounds per square inch gauge for 11.5 hours, employing an air feed rate of about 13 cubic feet of air per hour per pound of charge. An oxidate is obtained having a neutralization number of 343, a saponification number of 515 and containing 2.8 percent by weight of non-saponifiable material. This oxidate is water washed twice, employing about twice its weight of water each time, at a temperature of -170 F., with settling and separating the water fraction containing dissolved oxygenates. The water washing results in a lowering of the neutralization number to 232.

The mineral lubricating oil is a blend in about a 40-60 ratio by weight respectively of a refined paraffinic residual oil having a Saybolt Universal viscosity at 210 F. of about seconds and a refined paraffinic distillate fraction having a Saybolt Universal viscosity at 100 F. of about 182 seconds.

The grease is prepared by mixing the organo-clay and oxidate into the mineral lubricating oil and milling in a Premier Colloid Mill with one pass at 0.003 inch clearance. A grease is obtained having an ASTM worked penetration at 77 F. of 355 and a dropping point of 500+ F.

Table I below shows the efiect of the oxidate in the above grease as an extreme pressure additive, with comparative data obtained upon the same base grease contaming 5 percent by weight of an oxidate of a different type. This was an acid-type oxidate having a high neutralization number of 311, a saponification number of 482 and a Saybolt Universal viscosity at 210 F. of about 6 6, obtained by oxidizing a refined pa-rafiinic distillate orl having a Saybolt Universal viscosity at 100 F. of about 150 seconds.

materials in the indicated proportions in percent by weight:

Estersil 10.0 Oxidate 5.0 Water V 0.1 Mineral lubricating oil Remainder The mineral lubricating oil is a residual fraction of about 84 seconds Saybolt Universal viscosity at 210 F. from a mixed base crude.

The estersil is a finely divided amorphous silica which has been made oil wettable and water resistant by esterification of the surface with butanol. It has a particle size of 8-10 millimicrons and comprises 88-89 percent silica.

The oxidate is a material obtained by oxidizing a slack wax having an oil content of 6 percent. The oxidation is carried out in an aluminum reactor by passing air through the wax containing 0.1 percent by Weight of potassium permanganate at 330 F. under a pressure of 65 pounds per square inch for 5.5 hours, employing an air feed rate of 15 cubic feet of air per hour per pound of charge. An oxidate is obtained having a saponification number of 35, a neutralization number of 294, a viscosity of 369 seconds Saybolt Universal at 210 F., and containing 4.1 percent by weight of unsaponifiable material. This oxidate is employed in the grease without separation of any oxidate fractions.

The grease is prepared by mixing together the above materials in the indicated proportions and circulating the mixture for one hour in a Manton-Gaulin homogenizer, with valve settings at 5000 and 2500 pounds.

A smooth :buttery grease is obtained having an ASTM worked penetration at 77 F. of 338 and an OK. Timken test of 40 pounds, as compared to an OK. Timken test of pounds for the base grease without the oxidate. The same grease containing 10 percent by weight of sulfurized lard oil in place of the oxidate typically gives an ASTM worked penetration at 77 F. of 358 [and scores at 30 pounds in the Timken test.

EXAMPLE III A grease representative of a preferred embodiment of this invention is obtained iii-om the following materials in the indicated proportions in percent by weight:

Organo clay 7-12 Sul-furized lard oi-l 5-15 Tricresyl phosphate 0.5-3.0 Oxidate 2-10 Mineral lubricating oil Remainder The grease is prepared as described in Example I, employing the same organo-clay and mineral lubricating oil. The tricresyl phosphate is employed in the composition as an anti-wear agent. The sulfurized lard oil is a product obtained by heating lard oil with sulfur in the conventional manner. Typical tests upon this material include a gravity, API, of 12.8, a Saybolt Universal viscosity at 210 F. of 258 seconds and a sulfur content of 7.73 percent. The oxidate is a highly oxidized waxate of the type described hereinabove as suitable oxidates [for use in accordance with this invention.

The following table shows typical results obtained upon these greases containing 8 percent of the organo-clay, 10 percent of sulfurized lard oil, one percent of tricresyl phosphate, and various amounts of the highly oxidized waxates. Comparative data are included for greases of the same composition without the oxidate and also for those containing different oxidates of the conventional types which have been employed heretofore in lubricating compositions. All of the greases shown in the table also contained one percent by weight of finely divided carbon black as a colorant. that described in Example I. Oxidate B is a Water washed oxidate having a neutralization number of 182, a saponification number of 283, a non-saponifiable content of 16 percent by weight and a Saybolt Universal viscosity at 210 F. of about 56 seconds, obtained by oxidizing a wax of the same type as that employed in the production of oxidate A for 6.5 hours in an aluminum reactor at 270 F. and 65 pounds per square inch pressure in the presence of 0.4 percent potassium permanganate, employing an air feed rate of 20 cubic feet per hour per pound of charge. Oxidate C is a material having a neutralization number of 101 and a saponification number of 211, which is the water washed fraction of an oxidate obtained by the oxidation of a refined parafiinic distillate oil having a Saybolt Universal viscosity at F. of about 150 seconds. Oxidate D is a material having a neutralization number of 50 and a saponification number of 193, which is the water washed fraction of an oxidate obtained by oxidizing a -427 F. melting point par-affin wax to a limited extent and under conditions giving an ester type product. Oxidate E is a high viscosity ester-type oxidate, having a Saybolt Universal viscosity at 210 F. of 43109 seconds, obtained by oxidizing petrolatum from a mixed base heavy residium.

Table II Timken Test Oxidate 0.11. Score As shown by the data given in the above table, the Timken values of these greases are increased by small amounts, upward from about 2 percent, of the high neutralization number oxidates A and B. Oxidates C, D, and E, representative of the oxidates which have been employed in lubricating compositions heretofore, give no improvement or even decrease the extreme pressure properties of this composition. The Timken tests obtained upon the compositions containing both sulfurized lard oil and oxidate A or B indicate that a synergistic effect is produced by the oxidate and the sulfurized lard oil in combination, since these values are far higher than those obtainable by using either of these additives alone as an extreme pressure agent.

EXAMPLE IV Another grease representative of the lubricating compositions of this invention is obtained from the following materials in the indicated proportions in percent by The wax oxidate is that described in Example I. The

In the table, oxidate A is.

sulfurized sperm oil is a commercial additive containing about percent by weight of sulfur, obtained by heating sperm oil with about 8-15 percent of sulfur at 350- 400 F. for about 1-3 hours. The mineral lubricating oil is a blend in about a 1:1 ratio by Weight of a refined wax distillate oil having a Saybolt Universal viscosity of about 182 seconds at 100 F. and a refined Manvel residual oil having a Saybolt Universal viscosity of about 82 seconds at 210 F.

The grease preparation is carried out by the method involving saponification in situ in the presence of about /2 of the mineral lubricating oil employed in the grease, dehydrating, adding an additional 7 of the lubricating oil, heating the mixture to melting, and quenching with the remainder of the mineral lubricating oil. The saponification is carried out by heating a methyl ester of 12-hydroxystearic acid, sold commercially as Paricin-l, with aqueous lithium hydroxide in the presence of the mineral lubricating oil at 180200 F. for one hour. The dehydration is carried out by heating the mixture to about 300 F., and the melting by further heating to about 400 F. The heating is then discontinued and the mass quenched at a rate below 15 F. per minute by adding the remainder of the lubricating oil at room temperature. The additives are incorporated into the grease mixture While it is at a temperature of about 200-220 F. The grease is finished by milling in at Charlotte colloid mill at 0.006 inch clearance.

A grease prepared as described above is a soft smooth grease having an ASTM worked penetration of 347, and a Timlren test of OK. 70 pounds, score 80 pounds, as compared to 40 and 45 pounds, respectively, for the base grease without the oxidate.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and only Such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A lubricating composition comprising a mineral lubricating oil in major proportion having incorporated therein about 0.515 percent by Weight of a wax oxidate having a neutralization number of about 150-550, a ratio of neutralization number to saponification number of at least 0.5, and comprising in at least a major proportion compounds containing more than 3 carbon atoms per molecule, obtained by reacting a paraflin Wax separated from a parafiinic distillate petroleum oil with air at a temperature in the range of 200 F.400 F., under a pressure of about 30-500 pounds per square inch gauge, and with an air feed rate of 10-60 cubic feet of air per hour per pound of wax charge until an oxidized product having a neutralization number in about the range 200-550 is obtained, said oxidate being present in the lubricating composition in sufficient amount to impart improved extreme pressure properties thereto.

2. A lubricating composition according to claim 1 containing about 2-10 percent by weight of the said oxidate.

3. A lubricating composition according to claim 1 wherein the said oxidate is a water washed oxidate frac tion.

4. A lubricating composition according to claim 1 wherein the said wax oxidate is obtained by reacting parafiin wax with air at a temperature in about the range 270 F.330 F. and under a pressure of about 50-250 pounds per square inch gauge.

5. A lubricating composition according to claim 1 wherein the said wax oxidate is obtained by Water washing a wax oxidate having a neutralization number in about the range 250-550 and a ratio of neutralization number to saponifica-tion number of at least about 0.6.

6. A lubricating composition according to claim 1 containing about 2-20 percent by weight of a sulfurized fatty oil.

7. A lubricating composition according to claim 6 containing about 0.53 percent by weight of tricresyl phosphate.

8. A lubricating composition according to claim 1 containing a gelling agent in suflicient amount to form a grease.

9. A lubricating composition according to claim 8 wherein the said gelling agent is a colloidal inorganic material having at least a substantial part of its surface coated with a hydrophobic organic compound.

10. A lubricating composition according to claim 8 wherein the said gelling agent is bentonite, which'has been treated with a quaternary ammonium compound containing at least one aliphatic hydrocarbon group containing at least 10 carbon atoms.

11. A lubricating composition according to claim 8 containing about 2-20 percent by weight of a sulfurized fattyoil.

12. A lubricating composition comprising a mineral lubricating oil in major proportion having incorporated therein about 2-10 percent by weight, suificient to impart improved extreme pressure properties to the composition, of an oxidate fraction having a neutralization number of about -550, obtained by water washing a parafiin wax oxidate having a neutralization number in about the range 250550 and a ratio of neutralization number to saponification number of at 'least about 0.6, said paraffin wax oxidate being obtained by reacting a parafiin wax containing less than about 10 percent by weight of oil with air in the presence of a metal permanganate catalyst and at a temperature in the range 250 F.350 F. and under a pressure of about 50-250 pounds per square inch gauge, with an air feed rate of 10-60 cubic feet of air per hour per pound of wax charge.

13. A lubricating composition according to claim 12 containing a gelling agent in sufiicient amount to form a grease, said gelling agent being selected from the class consisting of hydrophobic organo-treated silica and bentonite clays and metal soaps.

14. A lubricating composition according to claim 12 containing about 315 percent by Weight of a sulfurized fatty oil.

References Cited in the file of this patent UNITED STATES PATENTS 1,863,004 Burwell June 14, 1932 2,043,923 'Burwell June 9, 1936 2,243,420 Frolich May 27, 1941 2,249,333 Smith July 15, 1941 2,531,440 Jordan Nov. 28, 1950 2,652,365 Moore et a1 Sept. 15, 1953 2,812,306 Liehe Nov. 5, 1957 2,859,234 Clem Nov. 4, 1958 2,862,803 Oosterbout Dec. 2, 1958 2,881,140 Schrum Apr. 7, 1959 2,894,970 McKinley et al July 14, 1959 OTHER REFERENCES Boner: Manufacture and Application of Lubricating Greases, Reinhold Pub. Corp, N .Y., 1954, p. 738. 

1. A LUBRICATING COMPOSITION COMPRISING A MINERAL LUBRICATING OIL IN MAJOR PROPORTION HAVING INCORPORATED THEREIN ABOUT 0.5-15 PERCENT BY WEIGHT OF A WAX OXIDATE HAVING A NEUTRALIZATION NUMBER OF ABOUT 150-550, A RATIO OF NEUTRALIZATION NUMBER TO SAPONIFICATION NUMBER OF AT LEAST 0.5, AND COMPRISING IN AT LEAST A MAJOR PROPORTION COMPOUNDS CONTAINING MORE THAN 3 CARBON ATOMS PER MOLECULE, OBTAINED BY REACTING A PARAFFIN WAX SEPARATED FROM A PARAFFINIC DISTILLATE PETROLEUM OIL WITH AIR AT A TEMPERATURE IN THE RANE OF 200*F.-400*F., UNDER A PRESSURE OF ABOUT 30-500 POUNDS PER SQUARE INCH GAUGE, AND WITH AN AIR FEED RATE OF 10-60 CUBIC FEET OF AIR PER HOUR PER POUND OF WAX CHARGE UNTIL AN OXIDIZED PRODUCT HAVING A NEUTRALIZATION NUMBER IN ABOUT THE RANGE 200-550 IS OBTAINED, SAID OXIDATE BEING PRESENT IN THE LUBRICATING COMPOSITION IN SUFFICIENT AMOUNT TO IMPART IMPROVED EXTREME PRESSURE PROPERTIES THERETO. 